<script>
export default {
  name: "Pagination",
  props: {
    /* 当前第几页 */
    pageNo: {
      type: Number,
      required: true
    },
    /* 一页展示数据条数 */
    pageSize: {
      type: Number,
      required: true
    },
    /* 总共多少条数据 */
    total: {
      type: Number,
      default: 0
    },
    /* 连续页码数 */
    continues: {
      type: Number,
      required: true
    }
  },
  computed: {
    /* 总共的页数 */
    totalPage() {
      return Math.ceil(this.total / this.pageSize)
    },
    /* 连续页码数的起始数字和结束数字 */
    startAndEnd() {
      let start = 0, end = 0
      const {continues, totalPage, pageNo} = this
      // 不正常的现象，连续的页码数(continues)大于总共的页数(totalPage)
      if (continues > totalPage) {
        start = 1
        end = totalPage
      } else {
        // 正常的现象，总共的页数(totalPage)大于连续的页码数(continues)
        start = pageNo - Math.floor(continues / 2)
        end = pageNo + Math.floor(continues / 2)
        if (start < 1) {
          start = 1
          end = continues
        }
        if (end > totalPage) {
          start = totalPage - continues + 1
          end = totalPage
        }
      }
      return {start, end}
    }
  },
}
</script>

<template>
  <div class="pagination">
    <button :disabled="pageNo===1" @click="$emit('getPageNo',pageNo-1)">上一页</button>
    <button v-if="startAndEnd.start>1" @click="$emit('getPageNo',1)">1</button>
    <button v-if="startAndEnd.start>2">···</button>

    <template v-for="(page,index) in startAndEnd.end" v-if="page>=startAndEnd.start">
      <button @click="$emit('getPageNo',page)" :class="{active:pageNo-1===index}">{{ page }}</button>
    </template>

    <button v-if="startAndEnd.end<totalPage-1">···</button>
    <button v-if="startAndEnd.end<totalPage" @click="$emit('getPageNo',totalPage)">{{ totalPage }}</button>
    <button :disabled="pageNo===totalPage" @click="$emit('getPageNo',pageNo+1)">下一页</button>
    <button style="margin-left: 30px">共 {{ total }} 条</button>
  </div>

</template>

<style scoped lang="less">
.pagination {
  text-align: center;

  button {
    margin: 0 5px;
    background-color: #f4f4f5;
    color: #606266;
    outline: none;
    border-radius: 2px;
    padding: 0 4px;
    vertical-align: top;
    display: inline-block;
    font-size: 13px;
    min-width: 35.5px;
    height: 28px;
    line-height: 28px;
    cursor: pointer;
    box-sizing: border-box;
    text-align: center;
    border: 0;

    &[disabled] {
      color: #c0c4cc;
      cursor: not-allowed;
    }

    &.active {
      cursor: not-allowed;
      background-color: #c00000;
      color: #fff;
    }
  }
}

</style>
